TAU PHOSPHORYLATION IN ALZHEIMER'S DISEASE - Neuronal degeneration in Alzheimer's Disease, in advanced Down's Syndrome and in normal aging is probably caused at least in part by the formation of paired helical filaments and neurofibrillary tangles from phosphorylated cytoskeletal proteins, especially the microtubule-associated protein TAU. We plan to explore this model using our novel Neurofilament/TAU kinase which unexpectedly appears to be regulated by the concentration of free ATP. We will (1) determine precisely the phosphorylation sites in human TAU isoforms produced by our NF/Tau kinase, by other known protein kinases and by combinations of these kinases; (2) examine the role of phosphorylation, as explored in (1), in putative self-aggregation of human TAU and in microtubule assembly in the presence of TAU; (3) explore the role of free ATP in regulating the in vitro activity of our NF/Tau kinase; (4) test in cell culture the putative control of TAU phosphorylation by regulating the concentration of ATP; (5) locate by immunohistochemistry our human NF/TAU kinases to particular cell types of the human brain; (6) clone the cDNA for our bovine NF/TAU kinases to deduce their primary structure; (7) correlate Alzheimer dementia/pathology in translocation Down's syndrome individuals with particular regions of chromosome 21. Most of our experiments will use bovine NF/TAU kinase preparations, but native and recombinant human TAU as substrates. Neuronal degeneration during normal aging may thus be explained by an accumulation of mutations in mitochondrial DNA during the lifetime of a neuron, leading to a drastic reduction in ATP levels with consequent phosphorylation and PHF/NFT formation and eventual cell death. Our studies will confirm or modify the model.